Signal charged particle detectors such as electron detectors can be used for charged particle beam devices, e.g. electron microscopes for electron beam inspection (EBI), defect review or critical dimension measurement, focused ion beam systems etc. Signal charged particle detectors are for example used for the detection of electrons in scanning electron microscopes. Upon irradiation of a specimen or sample by a primary charged particle beam, signal charged particles, such as secondary electrons (SE), are created, which may carry information about the topography of the specimen, its chemical constituents, its electrostatic potential and others. In some particle detectors, the signal charged particles are collected and guided to a sensor, e.g., a scintillator, a pin diode or the like. An image can be created where the gray level is proportional to the number of signal charged particles collected.
In EBI, a bright field (BF) detector can be used which may not be sensitive enough to changes in topography or surface potentials (voltage contrast—VC). VC can for example be enhanced by energy filtering the signal charged particle signal, while topography information resulting from physical defects can be enhanced using multiple sensors that collect only signal charged particles within certain ranges of take-off angles at the specimen. Topography detectors can be divided into four or more segments (with or without a central BF area), which can be read separately. The signals can then be combined (e.g. subtracted) to enhance contrast.
For multi perspective imaging, including energy filtering or angular filtering, the information carried by the signal charged particles should be conserved while the signal charged particle beam is transferred from the specimen to the signal charged particle detector. This can be done by an optical system (signal charged particle optics, e.g., SE optics) having a plurality of optical components. EBI should provide a high throughput, which can, for instance, be increased by using multiple beamlets simultaneously in one column to scan the specimen.
Aberrations can occur in signal charged particle optics, e.g., in a hemispherical beam bender or sector beam bender (SBB) used to deflect the signal charged particle beam. With increasing width of the signal charged particle beam inside the SBB, the signal charged particle beam is deformed. For multiple beamlets, the lateral position of the beamlets in the focus plane shows a considerable amount of distortion.
In view of the above, new signal charged particle deflection devices that overcome at least some of the problems in the art are beneficial. In particular, signal charged particle deflection devices providing improved focusing, angular resolution, detection efficiency, and minimized distortion of the signal charged particle beam are beneficial.